The project is an animal study of the pharmacokinetics and biochemistry of iodinated organic anions that are used or proposed for use as radiographic contrast materials for use in oral cholecystography and intravenous cholangiography. The purpose of the investigations are as follows: 1) To determine the most efficacious agent for use in clinical practice. 2) To determine how the agent can be used with maximum efficiency and safety in clinical practice. 3) To develop new agents. 4) To elaborate the precise excretory kinetics involved in the excretion of bilirubin and BSP. 5) To develop a reliable liver function study for clinical use. BIBLIOGRAPHIC REFERENCES: Berk, R.N., Loeb, P.M., Cobo-Frenkel, A., Barnhart, J.L. Saturation kinetics and choleretic effect of iodoxamate and iodipamide - two radiographic contrast materials for use in intravenous cholangiography: an experimental study in dogs, Radiology 119:529-537, June 1976.